The Richard Stockton College of New Jersey
Chemistry Program, School of Natural Sciences and Mathematics
PO Box 195, Pomoma, NJ
CHEM 3410: Physical Chemistry I — Fall 2008
In-class practice problems
October 22, 2008
1. Antimony trioxide Sb2O3, has two structurally different crystalline forms: cubic and orthorhombic
(ortho). Over a range of temperatures, the value of ∆µfor the change in state
Sb2O3(ortho, p = 1 bar, T )→Sb2O3(cubic, p = 1 bar, T )
is given by (in units of J, Tin Kelvin, and with ∆Cpnegligibly small):
∆µ(T, p = 1bar) = −5,815.+ 6.90T
(a) Which form of Sb2O3is thermodynamically stable at 298 K and 1 bar?
(b) At what temperature are the two forms in equilibrium at p=1 bar?
(c) The molar volumes of the cubic and orthorhombic forms are found to be Vcubic = 5.606 ×
10−5m3and Vortho = 5.141 ×10−5m3. Using the Clapeyron equation, calculate the slope
of the cubic-orthorhombic coexistence line (dP
dT ) in units of bar/K.
HINT: 1 J/m3= 10−5bar and ∆S=−∂∆µ
∂T P.
2. You synthesize a new drug with the following properties:
•The vapor pressure over the liquid phase (in bar) is given as:
ln Pl=−3010
T+ 13.2
•The vapor pressure over the solid phase (in bar) is given as:
ln Ps=−3820
T+ 16.1
(a) What is the temperature and pressure at the triple point?
(b) Is the solid, liquid, or gas stable at P= 1 bar and T= 298 K?
(c) Approximate ∆Hsublimation.
3. It has been suggested that the surface melting of ice plays a role in enabling speed skaters to achieve
peak performance. Carry out the following calculation to test this hypothesis. At 1 atm pressure,
ice melts at 273 K, ∆Hfusion = 6010 J/ mol, the density of ice is 920 kg/m3, and the density of
liquid water is 997 kg/m3. Also note that 1 bar = 105Pa.
(a) What pressure is required to lower the melting temperature by 5.0C?
(b) Assume that the width of the skate in contact with the ice has been reduced by sharpening
to 25 ? 103 cm, and that the length of the contact area is 15 cm. If a skater of mass 85 kg is
balanced on one skate, what pressure is exerted at the interface of the skate and the ice?
(c) What is the melting point of ice under this pressure?
(d) If the temperature of the ice is 5.0C, do you expect melting of the ice at the iceskate interface
to occur?